Human papillomavirus (HPV) related cancers, including cervical, vaginal, anal, and oropharyngeal are a significant burden on the US healthcare system that can be prevented through adolescent HPV vaccination. Despite the fact that clinical guidelines recommend vaccination for adolescent females and males, HPV vaccine coverage among US adolescents is suboptimal (in 2010, females: 49% for 1 dose and 32% for all 3 doses; males: 2% for 1 dose). Rates are lowest among traditionally underserved patients (uninsured, low income, racial and ethnic minorities) seen in safety-net healthcare settings. Many parents of adolescents are ambivalent about the vaccine and delay making a decision or talking with a provider about it. Self-persuasion -generating one's own arguments for a health behavior - may be particularly effective for parents who are undecided or not motivated to make a vaccine decision. Through three stages, we will identify an optimal and feasible self-persuasion intervention strategy to promote adolescent HPV vaccination in safety-net clinics. In Stage 1, we will learn about the content and scope of pro-vaccine arguments through: cognitive interviews conducted with parents (n=50) of patients and audio recordings of parent-provider HPV vaccine discussions (n=50) during clinic visits. In Stage 2, we will (a) use findings from Stage 1 to develop four self-persuasion intervention conditions that vary by cognitive processing level (parents verbalize vs. listen to arguments) and choice of argument topics (parents choose vs. are assigned topics) and (b) identify which intervention condition is optimal through a controlled proof of concept study (n = 160) that quantitatively examines basic self-persuasion mechanisms (cognitive processing, choice) and qualitatively explores experiences with intervention tasks. In Stage 3, we will conduct a pilot study (n = 90) in the safety-net clinics to assess feasibility of the optimal intervention condition identified in Stage 2. We will also assess its impact on parent-provider discussions. The research will result in a feasible and acceptable self-persuasion intervention that can impact public health through prevention of HPV-related cancers. Our interdisciplinary team will be positioned to conduct a future efficacy trial of the sef-persuasion HPV vaccine intervention for underserved, undecided parents of adolescents and develop clinic-based self-persuasion approaches for other cancer prevention behaviors.